from Hacker News

Daily energy expenditure through the human life course

by shartshooter on 10/14/23, 6:40 AM with 239 comments

• by tails4e on 10/14/23, 6:04 PM

  I've always been curious about my own metabolism. When I was a teenaeger / in university I ate pretty badly. Chocolate bars every day after lunch, loads of carbs, not to mention alcohol, etc etc. I was rail thin. I once got a body fat assesment when I joined a gym (I did no exercise at all and this was a brief attempt to get buff) and the person doing the test was shocked and couldn't pinch anything to measure. I had no fat. This lasted till I was 25 where seemingly overnight I then had to watch what I eat or I started to gain fat. So what explains this seeming inability to gain weight no matter what I ate, and in my mid twenties having a more normal response to junk food?

• by logicchains on 10/14/23, 2:40 PM

  Muscle burns more energy than fat. As people age, their muscle mass declines without sufficient exercise, so we'd naturally expect the average person's metabolism to decline via this even if "metabolism per kg muscle" didn't change.

• by dp-hackernews on 10/14/23, 1:18 PM

  No mention of how a persons lifestyle changes over that period though.

  Surely there is a correlation to the causation?

  The head-bone is connected to the neck-bone etc...

  You cannot study figures in isolation and expect them to yield some meaningful results while ignoring the influence of other figures upon those results.

  - Kids move around a lot, and they're still growing/developing

  - Teenagers move more constructively i.e. sports, and they're still growing/developing

  - Adults move a bit less, and have almost stopped growing/developing

  - Older adults try do keep moving, but with other life responsibilities it gets hard to put the same time in

  - Older adults become less and less bothered about moving

  - Even older adults have acquired illness and injuries and can't move as much

  Seems quite simple and obvious no? - Maybe...

  Those that don't fit the mould have some other reason that makes then more of an outlier to the norm.

  If life today didn't offer as much assistance as the past, we would all be a lot more healthy - not to mention more active, you know walking and manual work etc...

  Not to forget that the abundance of food (good and bad) will have a bearing on the results. Maybe the older people that can't afford as much food are the outliers - and better benchmark.

  Unless you are suffering from malnutrition, or you are overeating the wrong sort of food (good and bad) then your metabolism, unless affected by biological factors should be pretty stable.

  Isn't this what being in homeostasis means?

  Doesn't the body adapt to effects of S.A.I.D. - Specific Adaptations to Imposed Demands.

• by dp-hackernews on 10/14/23, 1:42 PM

  Did anyone happen to read any of the responses to the article at https://www.science.org/

  It seems that others don't fully support their findings either.

  https://www.science.org/doi/10.1126/science.abe5017#eletters...

• by dp-hackernews on 10/14/23, 2:34 PM

  * Extreme events reveal an alimentary limit on sustained maximal human energy expenditure.

  "We compiled measurements of total energy expenditure (TEE) and basal metabolic rate (BMR) from human endurance events and added new data from adults running ~250 km/week for 20 weeks in a transcontinental race. For events lasting 0.5 to 250+ days, SusMS decreases curvilinearly with event duration, plateauing below 3× BMR. This relationship differs from that of shorter events (e.g., marathons). Incorporating data from overfeeding studies, we find evidence for an alimentary energy supply limit in humans of ~2.5× BMR; greater expenditure requires drawing down the body’s energy stores. Transcontinental race data suggest that humans can partially reduce TEE during long events to extend endurance."

  https://www.science.org/doi/full/10.1126/sciadv.aaw0341

• by meindnoch on 10/14/23, 12:36 PM

  Another sobering result for the fitness industry, that convinces 30 year old men to be on TRT.

• by dfjkdksjds789 on 10/14/23, 12:24 PM

  Super useful outcome, especially given I find that people think that after reaching even young ages 24, 25 even begin thinking that metabolism has some extreme drop off right after reaching young adulthood

• by strangesmells02 on 10/14/23, 2:36 PM

  Anecdotally: I havent changed diet one bit, actually I eat way healthier than when I was younger.

  And still weigh much more than when younger.

• by paulpauper on 10/14/23, 2:36 PM

  I ain't buying it. There is a replication crisis in the sciences, and it would not surprise me if this is wrong too, or at least that the results do not mean what they are purported to mean. I have read many personal accounts here and elsewhere of men who were able to eat a lot in their late teens, 20s, and early 30s, and then suddenly by their 30s gain a lot of weight despite not changing their lifestyle or diet much.

  Inactivity alone does not explain it. Consider for example Bill Gate...according to his resume, in which he lists his precise height and weight, in his 20s he weighed just 125 pounds. It's evident he has put on a lot of weight, all in his mid-section, well before he turned 60. His job literally entailed sitting at a computer all day coding. If anything, given his philanthropy efforts and retirement, he is more active now than he was in his 20s when working full-time at Microsoft. Is he eating more? I doubt it.

  For so many people, celebrities for example, a switch is flipped in which there is sudden weight gain after the age of 30 or so, like John Travolta, Stevie Wonder and others. Because celebrities are photographed, you can see the weight progression and the abrupt jump in weight. Even with money for personal chefs and trainers, not gaining weight is hard.

  I can personally attest that if I ate the same quantity of food now as I did at 20 I would gain weight, and no I'm not 60. And I am just as active , maybe more so. So yeah not buying this study.

• by 0xDEAFBEAD on 10/14/23, 6:28 PM

  What's the age at which anti-aging interventions are most impactful?

  I assume they don't help much when you're young, because you're already healthy as a youth.

  Presumably waiting until you're on your deathbed to start high-intensity intervals is not the best idea either.

  Supposing a person had a limited budget of "anti-aging firepower" in the form of pills, exercise, etc. -- what age would be most impactful to apply it?

• by smileysteve on 10/14/23, 2:01 PM

  This doesn't seem to line up anecdotally;

  The first outlier I see is female health and PCOS, starting in mid 20s for women.

  The next outlier I see is insulin resistance and pre and diabetes based metabolism decline.

  From a hormone perspective, nose, ear, chin (femalr), and head hair seem to be going under significant change.

• by karmakaze on 10/14/23, 2:43 PM

  This is interesting for me to see. For the longest while I was wondering why through my 40s and later I didn't seem to be hit with middle-aged weight gain, all while living my sedentary life in the computer chair. I wouldn't classify myself as average though, I've always had low heart rate/low blood pressure and low blood sugar. Swimming in salt-water is fun because I can float without much effort.

  I did notice a decline in metabolism/muscle mass in the past several years, so I took to walking rather than driving in the city/neighbourhood and eating more and regularly which seems to have brought my levels back up somewhat. Now I look like someone who only goes to the gym on leg days.

• by ermir on 10/14/23, 1:43 PM

  This was completely expected, at the macro level this is easily observed by measuring the outputs of metabolism and bodily function, mainly heat and physical activity. All humans have a baseline bodily temperature, meaning that the inner metabolism also is the same across all humans.